In general the present invention relates to a cooler having at least one cooler module of the cooler which is curved to provide a gas turn module for turning run of the fiber web from its main running direction 80-190°.
As known from the prior art, fiber web producing processes typically comprise an assembly formed by a number of apparatuses arranged consecutively in the process line. A typical production and treatment line comprises a head box, a wire section and a press section as well as a subsequent drying section and a reel-up. The production and treatment line can further comprise other devices and/or sections for finishing the fiber web, for example, a pre-calender, a sizer, a final-calender, a coating section. The production and treatment line also typically comprises at least one slitter-winder for forming customer rolls as well as a roll packaging apparatus or a sheet cutter.
One problem with production of fiber webs is to achieve required surface properties and simultaneously achieve required bulkiness i.e. the relation of thickness of the web to its grammage (basis weight). When the fiber web has high bulkiness the basis weight can be reduced which results in considerable savings in raw material. Typically the fiber web is guided from the drying section to a pre-calender, when the temperature of the fiber web is about 80-90° C. In the thickness direction of the web the middle layers of the web are hot and near plastic state, whereby during calendering the fiber web will compact also in the middle layers, which leads to bulk loss. It is known from prior art that bulkiness can be saved in calendering by cooling the fiber web before calendering.
An object of the invention is to create a production line which is simple, cost effective and raw material saving for producing board and paper webs with high production capacity.
A further object of the present invention is to approach the above problems from a new point of view and to suggest novel solutions contrary to conventional modes of thinking.